Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$67.41	6.123%	$71.5375	$71.54	$71.55	$71.50
Purchase #2	$226.40	13.622%	$257.2402	$257.24	$257.25	$257.20
Purchase #3	$143.29	7.721%	$154.3534	$154.35	$154.35	$154.40
Purchase #4	$150.56	11.571%	$167.9813	$167.98	$168.00	$168.00
Purchase #5	$54.67	8.130%	$59.1147	$59.11	$59.10	$59.10
Purchase #6	$132.64	5.192%	$139.5267	$139.53	$139.55	$139.50
Purchase #7	$97.77	4.784%	$102.4473	$102.45	$102.45	$102.40
7 purchase totals =	$872.74		$952.2011	$952.20	$952.25	$952.10